The present invention is directed to a tool used for opening hollow core walls and ceilings to thereby allow access to the interior space of the wall or ceiling. The device includes a replaceable conventional pilot drill bit, a replaceable circular hole-cutting blade, (frequently referred to as a “hole saw,”) a flange member and a series of rebate blades located at angular positions on the flange.
A common manner for the construction interior walls in homes and office buildings is the attachment of gypsum board, also referred to as drywall and sheet rock, to structural members including studs, trusses and joists. Gypsum board is attached to upright studs to form walls and on the bottom of joists or trusses to form ceilings. These structural members are spaced at regular intervals and thereby this construction creates spaces between structural members. For example, in typical construction in the United States studs used in walls are spaced at 16 inch intervals. When the framing stage of construction is complete, mechanical contractors, including plumbers, electricians, phone service technicians, and heating and air condition workers may install lines and equipment within the walls. These lines may include phone lines, cable television lines,gas lines, water and sewer conduits, vacuum lines for central vacuum and heating and air conditioning ducts and control lines. When the mechanical contractors have completed the installation, insulation is installed in the exterior walls and top floor ceiling areas. Next gypsum boards are attached to the exposed studs and joists using glue, nails and/or screws. After the gypsum boards have been installed, the surface is finished using tape and joint compound. Finishing the gypsum board results in a smooth, continuous and seamless surface.
Frequently, after the finishing work as described above has been completed, there is a need to install additional components within the finished walls. A homeowner or tenant may also have a need to access internal lines to make repairs. For example, it may be desirable to add insulation to walls that border the exterior of a completed structure. In order to introduce insulation to these spaces, holes must be temporarily created within each cavity between the structural members. In any event, the installation of new components within the walls and ceilings, or accessing existing components within the walls or ceiling requires cutting open the gypsum board to provide such access. Upon the completing of the job, the access hole must then be patched and the surface refinished. One conventional manner in which to patch holes requires cutting the access hole so that two adjacent structural members are revealed. Next a piece of drywall is cut to closely conform to the opening and attached to the adjacent structural members. One disadvantage with this technique is that it is difficult to apply the joint compound over and within the seam between the abutting edges without creating a bulge around the patch. While the bulge can be slowly tapered out to make the repair almost imperceptible, this procedure involves additional finishing work, and may require multiple applications of the joint compound. This technique also requires the creation of fairly large access opening. An alternative repair technique taking a short piece of lumber and inserting the lumber through the access hole and then, attaching the lumber on the interior surface on opposite sides of the opening with a drywall screw so that the lumber spans the hole. A patch is then cut and attached to the lumber. This technique allows a smaller hole to be created but still requires cutting a patch to closely conform to the hole and the problem of finishing the surface without a bulge is not avoided.
Another problem with cutting though these surfaces with conventional power tools is that the technician runs a risk of inadvertently cutting into the lines. The accidental rupture of a power line or water line can leave considerable remedial work to reinstate the walls or flooring.
Although there a number of approaches to the problem of accessing interior spaces, including those not described in detail herein, there is a need for alternative and improved manners in which to access and patch hollow core structure. Preferably this access and subsequent patch and replacement procedure can be performed with a minimal amount of time, effort and expense.